The present invention relates to organic phosphonate and inorganic phosphate coatings covalently bonded to substrates having hydroxide-bearing surface layers. The present invention further relates to implantable medical devices having hydroxide-bearing surface layers covalently bonded to the organic phosphonate and inorganic phosphate coatings, which provide an osteoconductive surface on the medical device. In addition, the present invention relates to methods for forming such coatings, particularly on the surface of implantable medical devices having hydroxide-bearing surface layers, to provide an osteoconductive surface.
Creating a stable bond between bone tissue and the surface of metallic bone implants is a research topic of considerable interest. Poor bonding with the interface between the metallic surface of the implant and the bone tissue leads to low mechanical strength of the bone-to-implant junction and the possibility of subsequent implant failure.
Titanium and titanium alloys are used extensively as dental and orthopedic implants. Currently, there is no effective way to obtain strong attachment of incipient bone with the implant material at the interface between the surfaces of the two materials in order to xe2x80x9cstabilizexe2x80x9d the implant.
An important goal for interface optimization is to use species which are biocompatible and which enable bone mineralization at the interface following implantation. Bone tissue is a combination of protein and mineral content, with the mineral content being in the form of hydroxyapatite.
The problem of interface synthesis is often approached from the prospective of high temperature methods, including using plasma or laser-induced coating techniques. However, these methods engender problems of implant heating and surface coverage. For example, calcium phosphate deposition at high temperatures can give rise to ion migration. Plasma-induced phosphate coating of a titanium substrate gives surface hydroxyapatite as well as surface calcium phosphate, titanates and zirconates. Therefore, control of surface stoichiometry can be problematic, and defects at the interface may translate into poor mechanical strength.
The use of intermediate layers, for example of zirconium dioxide, to enhance hydroxyapatite adhesion and interface mechanical strength has been explored with success. However, a practical limitation involving laser or plasma deposition is that it is hard to obtain comprehensive coverage on a titanium implant of complex 3-dimensional structure. The zirconium dioxide interface formed at high temperatures is of low surface area and maintains few, if any, reactive functional groups for further surface modification chemistry.
Solution-phase surface processing does not suffer from the practical limitations of surface coverage that can be attendant with plasma or laser-based deposition methods, and procedures involving formation of hydroxyapatite from solution, often using sol-gel type processing, have been accomplished. Elegant methodologies have been developed in which graded interfaces have been prepared, extending from the pure implant metal to the biomaterial at the outer extremity by way of silicates. However, while solution-based procedures are inexpensive and give rise to materials resistant to dissolution by bodily fluids, adhesion of the hydroxyapatite to the implant metal is less strong than is observed when deposition is accomplished by plasma spraying techniques.
A need exists for a methodology that combines the benefits of the physical deposition of interfacial zirconium dioxide with the coverage, processing and speciation control of solution-based methods.
This need is met by the present invention. It has now been found that alkoxides of transition metals selected from Group IVB, Group VB and Group VIB of the Periodic Chart adhere to hydroxide-bearing substrate surfaces with relative ease. Such transition metal alkoxides thus may be used to form osteoconductive interfaces between bone tissue and implant materials. In particular, the transition metal alkoxides covalently bond phosphates and phosphonates to the surface hydroxyls of the implant substrate, which in turn provide an osteoconductive surface imparting enhanced mechanical strength and stability to bone-to-metal implant interaction. The phosphate or phosphonate interface functions to nucleate the growth of hydroxyapatite, thereby minimizing implant failure and the attendant need for serial revision implant surgery, which can be a consequence of unstable implant-to-bone interaction.
Therefore, in accordance with one embodiment of the present invention, there is provided a surface layer on a hydroxide bearing substrate, wherein transition metal atoms selected from Group IVB, Group VB or Group VIB of the Periodic Chart are covalently bonded to the surface hydroxyls of the substrate, and each transition metal atom is further covalently bonded to one or more ligands, thereby covalently bonding the ligands to the substrate surface. Preferred ligands include phosphate ligand, organic ligands of carboxylic and phosphonic acids containing between 2 and 20 carbon atoms, and ligands of pi-electron delocalized compounds. The phosphonic acid ligand may be functionalized to promote bonding to the protein content of bone tissue. Preferred pi-electron delocalized compounds include aromatic ring compounds with the preferred ligand being a phenolate.
Hydroxide-bearing substrates suitable for use with the present invention includes substrates having a native oxide surface layer, including the native oxide layers of metals and metal alloys. Single or mixed metal oxides may also be used. Native oxide layers of metalloids such as silicon are also appropriate. Surface modified ceramics and polymeric plastics may also be used.
While not being bound by any particular theory, it is believed, under ambient conditions, that in the absence of a transition metal atom interface, the ligands adhere to substrate hydroxides by hydrogen bonding, which is a weak interaction. The introduction of a transition metal interface makes a significant difference in the stability of the ligand surface layer by covalently bonding the ligand to the substrate surface. In particular, phosphoric and phosphonic acids react instantaneously and irreversibly under ambient conditions with surface-bound transition metal alkoxides to provide strong adhesion of the organic ligand layer to the surface. No such adhesion exists in the absence of the transition metal interface under ambient reaction conditions.
The present invention also provides a method by which ligands may be covalently bonded to the surface of hydroxide-bearing substrates. In accordance with this embodiment of the present invention, there is provided a method of forming a ligand layer on the surface of a hydroxide bearing substrate, which method includes the steps of:
providing a hydroxide-bearing substrate having a surface layer of alkoxides of transition metals selected from Group IVB, Group VB or Group VIB of the Periodic Chart covalently bonded thereto, wherein the alkoxides are bonded at the transition metal atoms to the surface hydroxyls of the substrate overlayer; and
reacting the transition metal alkoxide surface layer with a compound capable of reacting with the transition metal alkoxide to form a ligand covalently bonded to the transition metal, thereby forming a ligand layer on the surface of the substrate, covalently bonded at the transition metal atoms to the surface hydroxyls of the substrate.
Phosphate ligands are obtained by using phosphoric acid. Phosphonate ligands are obtained using organic phosphonates.
The hydroxide-bearing substrate is preferably provided with a transition metal alkoxide surface layer by reacting the substrate with a polyalkoxide of the transition metal having two or more alkoxide groups, so that the transition metal alkoxide surface layer is formed, covalently bonded to at least one surface hydroxyl of the substrate, and having at least one unreacted alkoxide group.
When phosphoric acid is used, transition metal monophosphate esters are formed that may be hydrolyzed to provide an inorganic transition metal polyphosphate coating. The coating structure is a two-dimensional network that on the surface of a dental or orthopedic implant is suitable for the ingrowth of bone tissue hydroxyapatite. Therefore, according to another embodiment of this aspect of the invention, the method of forming a ligand layer further includes the step of hydrolyzing a transition metal monophosphate ester surface layer so that an inorganic transition metal polyphosphate coating is formed on the substrate surface. Both the monophosphate and polyphosphate layers are rich in hydroxyl groups that are available for further chemical modification.
In a particularly preferred embodiment, phosphonic acids are chosen that form coatings, the organic ligand portions of which are functionalized at the omega-carbon to form covalent bonds with chemical precursors of bone tissue protein, such as amino acids, or with the bone tissue protein itself. The coatings typically self-assemble with the omega-carbon directed away from the substrate surface and available for covalent bonding or further chemical modification. Preferred omega-functional groups include amino, carboxylate and thiol groups.
This embodiment of the present invention thus obtains the adhesion properties of physical deposition methods under mild reaction conditions. In particular, the coatings according to this embodiment of the invention may be formed at ambient temperatures.
However, it has also been discovered that phosphate and phosphonate coatings may be directly covalently bonded to hydroxide-bearing substrates. The phosphate coatings are formed by heating substrates coated with phosphoric acid, while the phosphonate coatings are formed by heating substrates coated with organic phosphonic acids.
Therefore, in accordance with another embodiment of the present invention, there is provided a ligand surface layer on a hydroxide-bearing substrate in which phosphate or phosphonate ligands are covalently bonded to the substrate. The heating polymerizes the phosphonate ligands to form an organopolyphosphonate coating.
The present invention thus also provides a method by which phosphate and phosphonate Iigands may be covalently bonded to this surface of hydroxide-bearing substrates. In accordance with this embodiment of the present invention, there is provided a method of forming a phosphate or phosphonate ligand layer covalently bonded to the surface of a hydroxide-bearing substrate, which method includes the steps of:
coating a hydroxide-bearing substrate with phosphoric acid or an organic phosphonic acid; and
heating the coated substrate until the phosphoric acid or organic phosphonic acid covalently bonds to the substrate.
When the substrate is a metal or metal alloy, the phosphoric acid forms an inorganic phosphate coating that is rich in free hydroxyl groups. Like the transition metal monophosphate and polyphosphate coatings, the hydroxyl groups are available for further chemical modification. In each circumstance, the modification may be performed to introduce moieties for the attachment of chemical precursors of bone tissue proteins. For example, thiol compounds known to promote bone adhesion to gold metal implants may be covalently attached to the hydroxyl groups to form covalent linkages with bone tissue protein eliminating the need for the gold metal.
Transition metal oxide passivating coatings may also be formed by thermolysis or hydrolysis of the transition metal alkoxide surface layer, without first forming an organic ligand surface layer. The present invention therefore also includes an additional embodiment wherein there is provided a method of forming a transition metal oxide coating on an oxide-bearing surface, which method includes the steps of:
providing a hydroxide-bearing surface having a surface layer of alkoxides of transition metals selected from Group IVB, Group VB or Group VIB of the Periodic Chart covalently bonded thereto, wherein the alkoxides are bonded at the transition metal atoms to the surface hydroxides of the substrate overlayer; and
thermolyzing or hydrolyzing the transition metal alkoxides, so that a transition metal oxide coating is formed on the substrate surface, covalently bonded to the surface hydroxides of the substrate.
The present invention thus provides a novel type of interface that enables strong adhesion between a hydroxide-bearing surface and a ligand coating. The carboxylic acid ligands of the present invention have potential applications for structural surfaces as passivating coatings, providing paints or other passivating films with improved adhesion, or as lubricants. The organic coatings may undergo further synthesis to provide a thermal barrier or an electroactive material for electronics applications. The pi-electron delocalized ligand coatings of the present invention form electrically conductive layers without further treatment and have potential end uses as electroactive materials for electronics applications without further modification.
Furthermore, the present invention incorporates the discovery that the phosphate and phosphonate coatings of the present invention that are covalently bonded to the surface of an implantable medical device enhance the adhesion of bone tissue to the surface of the device. This is particularly useful for securely bonding replacement joints to bone tissue, as in the case of knee and hip replacements. Therefore, in addition to the coatings of the present invention, the present invention also provides methods for forming the coatings, coated implantable medical devices, methods for improving the adhesion to bone tissue of implantable medical devices, and methods for implanting medical devices by first coating them according to the present invention.
Other features of the present invention will be pointed out in the following description and claims, which disclose, by way of example, the principles of the invention and the best methods which have been presently contemplated for carrying them out.
The ligand surface layers according to the present invention are formed by reacting a hydroxide-bearing substrate having a transition metal alkoxide surface layer with a compound capable of reacting with the transition metal alkoxide to form a covalent bond between a ligand of the compound and the transition metal. The transition metal is selected from Group IVB, Group VB or Group VIB of the Periodic Chart. The alkoxides of this layer are covalently bonded by the transition metal to the surface hydroxides of the substrate.
By reacting compounds with the transition metal alkoxide layer, transition metal ligands form as a layer on the substrate surface, covalently bonded at the transition metal to the surface hydroxides of the substrate. The conditions under which the compounds are reacted with the transition metal alkoxide surface layer of the hydroxide-bearing substrate are not critical, and may be performed at ambient temperature and pressure. For example, a substrate having a transition metal alkoxide coating may be immersed in a solution containing an excess quantity of a compound such as a solution of a carboxylic acid, phosphoric acid, phosphonic acid or a suitable pi-electron delocalized compound in a non-polar solvent such as iso-octane. A dilute solution concentration of the compound should be employed, typically between about 1.0 mM and about 100 mM. The substrate will then be removed from the solution, rinsed with the iso-octane solvent, or another non-reactive solvent, and then dried to provide a substrate having an organic ligand surface layer.
Preferably, the compound is deposited on the transition metal alkoxide layer of the substrate using conventional vapor deposition techniques and equipment. The strength of the vacuum to be applied will depend upon the vapor pressure of the compound. Compounds with low vapor pressures will require a high vacuum.
Otherwise, ambient temperatures are employed, and an excess of the compound should be used to insure a complete reaction. Preferably, the transition metal alkoxide layer of the substrate should not be exposed to ambient moisture prior to being reacted.
The reaction proceeds by the transfer of a proton from the compound to the alkoxide of the transition metal, forming the corresponding alkanol and the ligand of the transition metal. Once the reaction is complete, the vacuum is maintained in order to draw off any excess of the compound and the alkanol byproduct.
Suitable compounds include, but are not limited to carboxylic acids, phosphoric acid, phosphonic acids and pi-electron delocalized compounds capable of reacting with a transition metal alkoxide to covalently bond a ligand of the compound to the transition metal. For purposes of the present invention xe2x80x9cphosphoric acidxe2x80x9d is defined according to its"" well-understood meaning, H3PO4. xe2x80x9cPhosphonic acidxe2x80x9d refers to compounds having the formula H2RPO3, wherein R is a hydrocarbon ligand with a carbon directly bonded to phosphorus.
Phosphoric acid coatings are covalently bonded as phosphate monoesters of the transition metal. The phosphate ligands may be hydrolyzed to form inorganic transition metal polyphosphate coatings on the substrate surface. The phosphate and polyphosphate coatings are rich in hydroxyl groups that are available for further chemical modification.
The inorganic transition metal phosphate monoesters also serve as a template for first chemical, then biological growth of bone tissue hydroxyapatite in the implant surface. Surface-bound inorganic transition metal phosphate monomeric units insinuate themselves directly into bone tissue hydroxyapatite to make a strong composite seal between the implant surface and the hydroxyapatite. Alternatively, the monoesters may be hydrolyzed to form inorganic transition metal polyphosphates having a two-dimensional structure, the monomeric units of which also insinuate themselves directly into bone tissue hydroxyapatite.
Essentially any organic carboxylic acid or phosphonic acid capable of forming a thin film on a hydroxide-bearing surface is suitable for use with the present invention. The carboxylic acids may be saturated or unsaturated, branched or unbranched, substituted or unsubstituted, and may be aromatic or non-aromatic. One example of a substituted carboxylic acid is a halogen-substituted carboxylic acid, with the preferred halogen being fluorine.
The carboxylic acid may be a monocarboxylic acid, dicarboxylic acid, or an anhydride of a dicarboxylic acid. Typical carboxylic acids will contain between 2 and 20 carbon atoms (exclusive of the carbonyl carbon), and preferably will contain between 3 and 18 carbon atoms. Stearic acid is one of the preferred carboxylic acids.
A preferred class of carboxylic acids are unsaturated carboxylic acids, which, after formation of the organic ligand surface layer may be polymerized to form polymeric surface layer. A preferred class of unsaturated carboxylic acids are the vinyl carboxylic acids such as acrylic acids, methacrylic acid, maleic acid, and the like. Halogen-substituted acrylates are preferred, particularly chlorine and fluorine, so that the resulting surface layer can be fully polymerized to obtain a poly (vinyl chloride) or fluoropolymer coating. Cinnamic acid could also be employed, so that the resulting surface layer could be fully polymerized to obtain a polystyrene coating.
Like the carboxylic acids, the phosphonic acid will have a hydrocarbon ligand that may be saturated or unsaturated, branched or unbranched, substituted or unsubstituted, and may be aromatic or non-aromatic. Typical hydrocarbon ligands of phosphonic acids will contain between two and twenty carbon atoms and preferably will contain between three and eighteen carbon atoms. Stearyl ligands are preferred.
A preferred class of ligands for phosphonic acids are omega-functionalized ligands that can be chemically transformed to react and covalently bond to chemical precursors of bone to protein, or the bone protein itself. Preferred omega functional groups include amino, carboxylate and thiol groups.
Essentially any pi-electron delocalized compound capable of reacting with a transition metal alkoxide to covalently bond a ligand of the ring compound to the transition metal is suitable for use with the present invention. Particularly useful compounds are pi-electron delocalized aromatic ring compounds. A particularly preferred aromatic ring compound is a phenol, which has a relatively acidic hydrogen that is readily transferred to the transition metal alkoxide to initiate a reaction that results in the formation of a transition metal phenolate. Five-membered heteroaromatic ring compounds having proton-donating ring substituents capable of reacting with the transition metal alkoxide are also desirable because of their high degree of pi-electron delocalization. Examples of such rings include furan, thiophene and pyrrole.
The hydroxide-bearing substrate having a transition metal alkoxide surface layer that is reactive with an organic compound to produce the organic ligand surface layers of the present invention is obtained by reacting the substrate with a transition metal polyalkoxide. Alkoxides of transition metals selected from Group IVB, Group VB and Group VIB of the Periodic Chart are suitable for use with the present invention, with Group IVB transition metals being preferred. Titanium (Ti) and Zirconium (Zr) are the preferred Group IVB transition metals, with Zr being most preferred.
Depending upon the position of the transition metal on the Periodic Chart, the transition metal alkoxide will have from two to six alkoxide groups. Preferred alkoxide groups have from 2 to 4 carbon atoms, such as ethoxide, propoxide, iso-propoxide, butoxide, iso-butoxide and tert-butoxides. Transition metal tetra-alkoxides are preferred, with the most preferred transition metal tetra-alkoxide being zirconium tetra tert-butoxide.
With Group IVB transition metal tetra-alkoxides, at least one of the alkoxide groups reacts with surface hydroxyls of the substrate to form covalent bonds between the surface hydroxyls and the transition metal. The reaction proceeds by proton transfer from the surface hydroxyls to an alkoxide group of a transition metal, producing an equivalent quantity of the corresponding alkanol. At least one alkoxide group does not react and remains available for reaction with organic compounds.
Group VB transition metals form penta-alkoxides and oxotrialkoxides that are suitable for use with the present invention. Both types of compounds also react by proton transfer to covalently bond the transition metal to substrate hydroxyls and produce an equivalent quantity of an alkanol byproduct. At least one alkoxide group does not react and is available for subsequent reaction with an organic compound. Group VB transition metals also form dioxo-monoalkoxides, which, if basic enough, will react with an acidic compound.
Group VIB transition metals form hexa-alkoxides, oxo-tetraalkoxides and dioxo-dialkoxides that are all suitable for use with the present invention. These compounds also react by proton transfer to covalently bond the transition metal to substrate hydroxyls, producing an equivalent quantity of an alkanol and leaving at least one unreacted alkoxide group for subsequent reaction with organic compounds.
Advantageously, many of the transition metal alkoxides suitable for use with the present invention are commercially available. This includes the preferred zirconium tetra tert-butoxide, which may be obtained from Aldrich Chemical. However the transition metal alkoxides may also be prepared by conventional techniques by reacting a halide or oxo-halide of the selected transition metal, depending on the desired number of alkoxide groups, with the corresponding alkoxide of a metal selected from Group I or Group II of the periodic chart.
The substrate may be reacted with the transition metal alkoxide by immersion in a dilute (1.0 mM to 100 mM) solution of the alkoxide in a non-reactive solvent, such as a lower alkane like iso-octane, a lower di-alkyl ether or tetrahydrofuran (THF). Or, again, the reaction may also be performed by vapor deposition. In both instances, an excess of transition metal alkoxide is employed, and the reaction then performed at ambient temperature. With solvent immersion, when the reaction is complete, the transition metal alkoxide layer obtained is rinsed with a solvent such as a lower alkane like iso-octane, a lower dialkyl ether, THF, and the like, and then dried. With vapor deposition, upon completion of the reaction the vacuum should once again be maintained to remove excess transition metal alkoxide and alkanol byproduct.
As noted above, the transition metal alkoxide layer formed on the substrate preferably should not be exposed to ambient moisture before being reacted with an organic compound. Therefore, a particularly preferred reaction is a two-stage vapor deposition process in which the transition metal alkoxide is first vapor deposited on the substrate. When the reaction is complete, vacuum is applied to remove excess transition metal alkoxide and alkanol by-product, which is then followed by vapor deposition of the organic compound, so that the transition metal alkoxide layer on the substrate is never exposed to ambient moisture. Upon completion of the reaction with the organic compound, the vacuum is then applied to withdraw excess organic compound and alkanol byproduct.
Substrates suitable for use with the present invention include any metal or metalloid capable of forming a native oxide overlayer, and essentially any substrate capable of being provided with an oxide overlayer coating by conventional techniques. The substrate may thus be a metal, alloy or metalloid with an actual native oxide overlayer, or a metal alloy or metalloid having an oxide overlayer physically produced by well-known oxidative conditions such as exposure to air and/or moisture. Dental and orthopedic implant substrates include titanium and alloys thereof such as Ti-6A1-4V. A non-metal or non-metalloid substrate such as a composite material may also be employed having an oxide of a metal deposited thereon by sputtering or having a silicon oxide overlay produced by applying a sol-gel to the substrate. Metal oxides may also be deposited on a metal or metal alloy substrate by sputtering.
The metal substrates on which oxide overlayers may be physically produced may be single or mixed metal materials. The preferred single metal substrates include aluminum and iron. Preferred substrates for bone implants include titanium and alloys thereof. Polymeric and ceramic materials may also be functionalized to covalently bond with transition metal alkoxides.
Indium tin oxide (ITO) is a non-native mixed metal oxide preferred for electronics end-use applications involving, for example, electrode processes. ITO is preferably applied to substrates by conventional techniques, such as sputtering. The preferred metalloid is silicon.
As noted above, the method of the present invention may be employed to prepare surface layers of polymerizable unsaturated carboxylic or phosphonic acids, such as acrylic phosphonic acid that may be subsequently polymerized to form a polymeric coating on the substrate. Unexpectedly, when acrylic acid and methacrylic acid are employed, the polymerization proceeds spontaneously upon exposure to air. For less reactive coatings, the polymerization can be performed by exposing the coating to conventional polymerization reagents and conditions.
The present invention also includes inorganic phosphate and organic phosphonate coatings that have been directly covalently bonded thereto. Inorganic phosphate coatings are prepared by coating metal-containing and metal alloy-containing substrates with a concentration of phosphoric acid effective to form a stable film on the substrate surface without excessively dissolving the substrate. This can readily be determined by those of ordinary skill in the art without undue experimentation. Phosphoric acid having a concentration between about 1.4 and about 2.8 M is preferred. Phosphonic acid coatings are similarly directly applied to a hydroxide-bearing substrate. These embodiments of the present invention advantageously eliminate a complicated process step requiring protection of a transition metal alkoxide coating layer from ambient moisture prior to the vacuum deposition.
The substrate is then heated to a temperature between about 40 and about 140xc2x0 C., with a temperature of about 90xc2x0 C. being preferred. Phosphate and phosphonate ligands then directly covalently bond to the substrate. The phosphonic acid ligands also polymerize to form organopolyphosphonate covalently bonded coatings.
Like the transition metal phosphate monoester and polyphosphate coatings, the inorganic phosphate coatings are rich in free hydroxyl groups. Each coating layer may be further functionalized to promote covalent attachment to bone tissue proteins, or precursors thereof, for example, by using thiol compounds conventionally employed to promote adhesion between gold metal implants and bone tissue. The hydrocarbon ligands of the organopolyphosphonate coatings may likewise be functionalized at the omega carbon as described above for phosphonate ligand coatings to form covalent bonds with chemical precursors of bone tissue protein or with the bone tissue protein itself.
The method of the present invention may also be employed to prepare passivating transition metal oxide coatings having improved substrate adhesion. Such transition metal oxide coatings are obtained by reacting the organic ligand coatings of the present invention with a basic solution capable of hydrolyzing the transition metal ligand, such as a 0.001 N to about a 1.0 N solution of a caustic material such as NaOH, KOH, NH4OH, and the like. Lewis bases capable of hydrolyzing the organic ligands may also be used. The transition metal alkoxide coatings may also be directly converted to transition metal oxide coatings, without first forming an organic ligand coating, by thermolysis of the transition metal alkoxide coatings at temperatures above 300xc2x0 K, preferably between about 400xc2x0 K and about 500xc2x0 K.
The phosphate and phosphonate coatings of the present invention are advantageously employed to provide osteoconductive surfaces for dental and osteopathic implants that exhibit improved adhesion at the bone tissue interface. The coatings can be applied to essentially any implant intended for bone or dental tissue contact fabricated from a material having a hydroxide-bearing surface at the intended bone or cental tissue interface. Implants made of titanium and alloys thereof may be employed, as well as aluminum or iron, and alloys thereof, and the like. Plastic polymer and ceramic materials with hydroxyl group-modified surfaces at the bone tissue interface may also be employed.
Ligand replacement reactions in the coordination sphere of surface transition metal complexes also make it possible to attach bio-compatible or bio-active organic co-polymers to implant surfaces. The purposes can range from implant lubrication or reduction of adhesion to the delivery of organic phase-soluble drugs at the implant-bone tissue interface.
The new methodology of the present invention enables strong adhesion between a dental or osteopathic implant and incipient bone tissue via a network of strong chemical bonds. Implant devices can be fabricated and surface processed ex-situ to assemble composite coatings on the implant surfaces that will give rise to a strong, non-fracturable bone-to-implant seal following implantation. The methodology is amenable to vapor-phase or solution-phase (aerosol spray-on) chemistry and proceeds under mild conditions, especially compared to plasma or laser-induced deposition.